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Cosmic Tails (That Aren’t From Comets)
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MLA Full: | "Cosmic Tails (That Aren’t From Comets)." YouTube, uploaded by SciShow, 3 April 2024, www.youtube.com/watch?v=5nDTOHWYwe4. |
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SciShow, "Cosmic Tails (That Aren’t From Comets).", April 3, 2024, YouTube, 12:02, https://youtube.com/watch?v=5nDTOHWYwe4. |
Comets are famous for having space tails. But they're not the only ones! Asteroids, planets, and even stars can rock tails of their own.
Hosted by: Stefan Chin (he/him)
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Sources:
https://science.nasa.gov/solar-system/comets/facts/
https://www.nasa.gov/directorates/smd/whats-the-difference-between-asteroids-comets-and-meteors-we-asked-a-nasa-scientist-episode-16/
https://www.nasa.gov/solar-system/asteroids-comet-like-tail-is-not-made-of-dust-solar-observatories-reveal/
https://science.nasa.gov/solar-system/meteors-meteorites/geminids/
https://www.jpl.nasa.gov/news/fizzing-sodium-could-explain-asteroid-phaethons-cometlike-activity
https://iopscience.iop.org/article/10.3847/PSJ/acc866
https://www.livescience.com/space/mercury/see-mercurys-giant-comet-like-tail-in-stunning-new-image-as-it-passes-close-to-the-sun
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020JE006671
https://www.nytimes.com/2021/03/04/science/moon-tail-beam.html
https://www.newscientist.com/article/dn27275-the-moons-got-two-tails-and-its-friends-might-too/
https://earthsky.org/space/how-to-capture-mercurys-sodium-tail/
https://www.sciencealert.com/the-tail-of-mercury
https://www.forbes.com/sites/startswithabang/2016/09/14/thats-no-comet-thats-pluto-comet-like-tail-and-x-rays-discovered-at-solar-systems-edge/?sh=5f7ed50df21a
https://chandra.si.edu/photo/2016/pluto/
https://chandra.si.edu/press/16_releases/press_091416.html
https://www.sciencedirect.com/science/article/abs/pii/S0019103516304031
https://www.space.com/30001-pluto-atmosphere-swept-comet-tail.html
https://www.keckobservatory.org/wasp-69b/
https://iopscience.iop.org/article/10.3847/1538-4357/ad11d0
https://iopscience.iop.org/article/10.1086/589968/meta
https://www.nature.com/articles/nature06003
https://ui.adsabs.harvard.edu/abs/2005ApJ...619L...1M/abstract
Images:
https://www.gettyimages.com/
https://bit.ly/3IXiTzs
https://commons.wikimedia.org/wiki/File:Comet_Hale-Bopp_Phot-mar14-hbs-2.jpg
https://commons.wikimedia.org/wiki/File:PIA22185.gif
https://bit.ly/4abI2lU
https://commons.wikimedia.org/wiki/File:Asteroid_3200_Phaethon_(1983_TB).gif
https://commons.wikimedia.org/wiki/File:Animation_of_3200_Phaethon_orbit.gif
https://bit.ly/3IW2bAw
https://www.eurekalert.org/multimedia/988744
https://commons.wikimedia.org/wiki/File:Mercury_Sodium_Tail.png
https://www.gettyimages.com/detail/photo/sun-and-moon-behind-mountain-royalty-free-image/92117497?phrase=sun+and+moon&adppopup=true
https://commons.wikimedia.org/wiki/File:Sodium-glow.jpg
https://commons.wikimedia.org/wiki/File:North_pole_of_Mercury_--_NASA.jpg
https://www.nasa.gov/image-article/plutos-brilliant-heart/
https://commons.wikimedia.org/wiki/File:15-011a-NewHorizons-PlutoFlyby-ArtistConcept-14July2015-20150115.jpg
https://commons.wikimedia.org/wiki/File:Blue_hazes_over_backlit_Pluto.jpg
https://chandra.harvard.edu/resources/illustrations/x-raysLight.html
https://commons.wikimedia.org/wiki/File:Chandra_artist_illustration.jpg
https://commons.wikimedia.org/wiki/File:PIA21061-Pluto-DwarfPlanet-XRays-20160914.jpg
https://commons.wikimedia.org/wiki/File:MVIC_sunset_scan_of_Pluto.jpg
https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2016JA022599
https://www.eurekalert.org/multimedia/1011323
https://exoplanets.nasa.gov/exoplanet-catalog/5142/wasp-69-b/
https://iopscience.iop.org/article/10.3847/1538-4357/ad11d0#apjad11d0f6
https://commons.wikimedia.org/wiki/File:Keck_Telescopes._Mauna_Kea_Summit_-_panoramio.jpg
https://svs.gsfc.nasa.gov/14359/
https://exoplanets.nasa.gov/exoplanet-catalog/5142/wasp-69-b/
https://exoplanets.nasa.gov/resources/2137/excess-hot-jupiters/
https://www.jpl.nasa.gov/images/pia09961-miras-tail-there-all-along
https://commons.wikimedia.org/wiki/File:Mira-uv-bow-shock-tail-vertical.jpg
http://www.galex.caltech.edu/media/glx2007-04r_img05.html
https://commons.wikimedia.org/wiki/File:GALEX_spacecraft_model.png
https://www.jpl.nasa.gov/images/pia09961-miras-tail-there-all-along
https://www.eso.org/public/videos/eso1919c/
Hosted by: Stefan Chin (he/him)
----------
Support SciShow by becoming a patron on Patreon: https://www.patreon.com/scishow
----------
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever: Adam Brainard, Alex Hackman, Ash, Benjamin Carleski, Bryan Cloer, charles george, Chris Mackey, Chris Peters, Christoph Schwanke, Christopher R Boucher, DrakoEsper, Eric Jensen, Friso, Garrett Galloway, Harrison Mills, J. Copen, Jaap Westera, Jason A Saslow, Jeffrey Mckishen, Jeremy Mattern, Kenny Wilson, Kevin Bealer, Kevin Knupp, Lyndsay Brown, Matt Curls, Michelle Dove, Piya Shedden, Rizwan Kassim, Sam Lutfi
----------
Looking for SciShow elsewhere on the internet?
SciShow Tangents Podcast: https://scishow-tangents.simplecast.com/
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Facebook: http://www.facebook.com/scishow
#SciShow #science #education #learning #complexly
----------
Sources:
https://science.nasa.gov/solar-system/comets/facts/
https://www.nasa.gov/directorates/smd/whats-the-difference-between-asteroids-comets-and-meteors-we-asked-a-nasa-scientist-episode-16/
https://www.nasa.gov/solar-system/asteroids-comet-like-tail-is-not-made-of-dust-solar-observatories-reveal/
https://science.nasa.gov/solar-system/meteors-meteorites/geminids/
https://www.jpl.nasa.gov/news/fizzing-sodium-could-explain-asteroid-phaethons-cometlike-activity
https://iopscience.iop.org/article/10.3847/PSJ/acc866
https://www.livescience.com/space/mercury/see-mercurys-giant-comet-like-tail-in-stunning-new-image-as-it-passes-close-to-the-sun
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020JE006671
https://www.nytimes.com/2021/03/04/science/moon-tail-beam.html
https://www.newscientist.com/article/dn27275-the-moons-got-two-tails-and-its-friends-might-too/
https://earthsky.org/space/how-to-capture-mercurys-sodium-tail/
https://www.sciencealert.com/the-tail-of-mercury
https://www.forbes.com/sites/startswithabang/2016/09/14/thats-no-comet-thats-pluto-comet-like-tail-and-x-rays-discovered-at-solar-systems-edge/?sh=5f7ed50df21a
https://chandra.si.edu/photo/2016/pluto/
https://chandra.si.edu/press/16_releases/press_091416.html
https://www.sciencedirect.com/science/article/abs/pii/S0019103516304031
https://www.space.com/30001-pluto-atmosphere-swept-comet-tail.html
https://www.keckobservatory.org/wasp-69b/
https://iopscience.iop.org/article/10.3847/1538-4357/ad11d0
https://iopscience.iop.org/article/10.1086/589968/meta
https://www.nature.com/articles/nature06003
https://ui.adsabs.harvard.edu/abs/2005ApJ...619L...1M/abstract
Images:
https://www.gettyimages.com/
https://bit.ly/3IXiTzs
https://commons.wikimedia.org/wiki/File:Comet_Hale-Bopp_Phot-mar14-hbs-2.jpg
https://commons.wikimedia.org/wiki/File:PIA22185.gif
https://bit.ly/4abI2lU
https://commons.wikimedia.org/wiki/File:Asteroid_3200_Phaethon_(1983_TB).gif
https://commons.wikimedia.org/wiki/File:Animation_of_3200_Phaethon_orbit.gif
https://bit.ly/3IW2bAw
https://www.eurekalert.org/multimedia/988744
https://commons.wikimedia.org/wiki/File:Mercury_Sodium_Tail.png
https://www.gettyimages.com/detail/photo/sun-and-moon-behind-mountain-royalty-free-image/92117497?phrase=sun+and+moon&adppopup=true
https://commons.wikimedia.org/wiki/File:Sodium-glow.jpg
https://commons.wikimedia.org/wiki/File:North_pole_of_Mercury_--_NASA.jpg
https://www.nasa.gov/image-article/plutos-brilliant-heart/
https://commons.wikimedia.org/wiki/File:15-011a-NewHorizons-PlutoFlyby-ArtistConcept-14July2015-20150115.jpg
https://commons.wikimedia.org/wiki/File:Blue_hazes_over_backlit_Pluto.jpg
https://chandra.harvard.edu/resources/illustrations/x-raysLight.html
https://commons.wikimedia.org/wiki/File:Chandra_artist_illustration.jpg
https://commons.wikimedia.org/wiki/File:PIA21061-Pluto-DwarfPlanet-XRays-20160914.jpg
https://commons.wikimedia.org/wiki/File:MVIC_sunset_scan_of_Pluto.jpg
https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2016JA022599
https://www.eurekalert.org/multimedia/1011323
https://exoplanets.nasa.gov/exoplanet-catalog/5142/wasp-69-b/
https://iopscience.iop.org/article/10.3847/1538-4357/ad11d0#apjad11d0f6
https://commons.wikimedia.org/wiki/File:Keck_Telescopes._Mauna_Kea_Summit_-_panoramio.jpg
https://svs.gsfc.nasa.gov/14359/
https://exoplanets.nasa.gov/exoplanet-catalog/5142/wasp-69-b/
https://exoplanets.nasa.gov/resources/2137/excess-hot-jupiters/
https://www.jpl.nasa.gov/images/pia09961-miras-tail-there-all-along
https://commons.wikimedia.org/wiki/File:Mira-uv-bow-shock-tail-vertical.jpg
http://www.galex.caltech.edu/media/glx2007-04r_img05.html
https://commons.wikimedia.org/wiki/File:GALEX_spacecraft_model.png
https://www.jpl.nasa.gov/images/pia09961-miras-tail-there-all-along
https://www.eso.org/public/videos/eso1919c/
Unless you’ve, kind of, stumbled into a certain kind of disaster movie, seeing a comet in the sky is a wonderful treat.
I mean that tail? Spectacular.
You’re not gonna find those anywhere else. Or are you? Well to human eyes, from Earth’s vantage point, the tail of a great comet can’t be beat.
But comets are far from the only cosmic bodies that can grow a tail. Here are five other cosmic wonders that leave a little bit of themselves behind as they careen through space. [♪ INTRO] In the grand scheme of the universe, comets and asteroids are pretty similar. I mean, asteroids are generally more rocky, and comets are more icy, but they’re both small clumps of stuff left over from our solar system forming a bunch of planets.
But comets are known for growing tails when they get too close to the Sun, and asteroids are not. When our Sun heats up a comet, a bunch of ice and dust get vaporized into a sort of temporary atmosphere called a coma. That coma is then blasted off the space rock by solar radiation to create a vibrant and reflective light show.
But there’s nothing stopping an asteroid from having stuff that the Sun can blast away, too. So several asteroids in our solar system are known to have comet-like traits. And one classic example is Phaethon, which has shed so much material over the eons that its debris cloud is thought to be the source of the Geminid meteor shower.
Usually, making a meteor shower debris cloud is a comet’s job. But you try telling Phaeton what to do. Astronomers have known about Phaethon’s tail since 2009.
And for a long time, they assumed it was made out of dust. Which makes sense, right? Comets have tails full of dust, and Phaethon likes to cosplay as a comet.
But upon closer inspection, Phaethon’s tail was way too robust to be made of just dust. So, there had to be something else going on. And eventually, astronomers managed to figure out that the tail was mostly made of sodium vapor.
See, Phaethon doesn’t just get a bit too close to the Sun. It gets closer to the Sun than Mercury, and far closer than any other notable asteroid ever does. And because it gets so close, it gets so hot that sodium inside the asteroid gets turned into a vapor, and eventually leaks up through the rest of the rock until it escapes and gets shaped into a tail.
Since comets can also release sodium vapor, you’d think we would have figured out this was happening to Phaethon a while ago. But no, the paper that actually proved it was happening was published in 2023. And although the paper answered one question, it raised others.
Like, if it’s not trailing a bunch of dust and pebbles and such, how did Phaethon make the debris cloud that the Geminids are coming from? The team did have a possible answer to that: Maybe there was some ancient collision between Phaethon and another body. But what that body was, and when that collision happened is still just a bunch of shrug emojis.
And Phaethon isn’t the only solar system body rocking a sodium-powered tail. As I mentioned before, comets can shoot out sodium vapor. But our next entry is a tag team of two much, much larger objects.
They’re so large their gravity has smushed them each into spheres. Dead, dark grey spheres. Of course I’m talking about Mercury and the Moon.
Mercury’s sodium tail was discovered back in 2001. And just like Phaethon, it's produced by the Sun’s heat. But it does have its own mystery.
Because Mercury’s tail isn’t at its brightest when it’s closest to the Sun. It’s actually brightest exactly 16 Earth days after that. And astronomers don’t know why.
Meanwhile, our moon is much further away, but that doesn’t stop it from shedding a bunch of sodium that the Sun’s radiation shapes into a long tail, too! And since the Moon orbits the Earth, there are a few days each lunar month… a few days around each New Moon… where our planet actually passes through that tail. During this time, the Earth’s gravity even causes some of that sodium to narrow in on a particular part of the sky.
And because sodium glows a particular shade of yellow, this means we see a greater concentration of yellow light in one patch of sky, about five times bigger than the Moon appears to be. Astronomers call it the Sodium Moon Spot. But before you get your hopes up, its light is way too dim for you to see it with the naked eye.
But it’s worth mentioning that the Moon’s tail isn’t just made out of sodium. Nor is Mercury’s. Sodium is just better at making its presence known, in the form of that yellow light.
And that makes it a good way to study the tail as a whole. For example, scientists want to understand how Mercury’s barely-there atmosphere changes as the Sun gets more or less active throughout the year. And as far as our lunar companion goes, studying the Sodium Moon Spot can help astronomers understand what’s creating the Moon’s tail at all.
Because according to research published in 2021, the spot doesn’t seem to get brighter when the Sun is more active. It does get brighter when the lunar surface is getting pelted by more micrometeoroids, though. So maybe its origin story is a bit different from Mercury’s, despite the two bodies looking so similar at first glance.
But lest you think tails are an Inner Solar System phenomenon, let’s turn our attention to Pluto. Because if any rock in the solar system is going to have a tail, it had better be the one that shares its name with a cartoon dog. When the New Horizons spacecraft flew by in 2015, astronomers got an up-close-if-not-personal look at Pluto’s tail.
And despite the dwarf planet being basically five billion kilometers from the center of the solar system, our Sun is still up to its old tricks. Its radiation is definitely a lot more spread out at those distances, but there’s still enough to smash into Pluto’s thin atmosphere and push molecules like nitrogen and methane into a tail. And on top of that, the collisions between the Sun’s particles and Pluto’s can knock electrons from one particle over to another.
It’s a process called charge exchange, and those electrons wind up having so much excess energy that they have to emit x-rays in order to calm down. I mean, as much as a subatomic particle can experience a sense of calm. It’s these x-rays that researchers used to discover Pluto’s tail in the first place.
But they started hunting for it before New Horizons made its closest approach. See, astronomers already knew that comets give off x-rays for the exact same reason. So in 2014, they used the Chandra X-ray Observatory to see if Pluto had them, too.
And after staring straight at Pluto for almost 10 hours, Chandra captured a whopping two x-rays. Which sounds like nothing. But it’s not.
It’s two more than nothing. And two whole x-rays can be a significant amount to an x-ray astronomer. But by combining that Chandra research with New Horizons’ data, scientists stumbled into a bit of a mystery: Pluto’s tail seems to be too bright.
Because while it’s shedding enough atmosphere into its tail, the Sun’s influence shouldn’t be strong enough to create that many x-rays. This could just mean that Pluto’s tail is actually bigger than New Horizons measured it to be. Or maybe there are some weird magnetic goings on in the region that are funneling the Sun’s radiation toward Pluto.
We’ll have to wait for a more sensitive x-ray telescope to take a look. Which…could be a while, so let’s move on to a tail that is way more impressive than anything a dwarf planet could hope to wag. This is WASP-69b, or at least an artist’s rendition of WASP-69b.
It’s roughly 160 light years away. And it orbits so close to its star, one of its years lasts less than four of our days. Given what we’ve learned about our Sun and bodies like Phaethon and Mercury, it should come as no surprise that WASP-69b’s star is slowly stripping off the exoplanet’s atmosphere and turning it into a tail.
But WASP-69b is a gas giant that’s larger than Jupiter, and about as massive as Saturn. So unlike Phaethon and Mercury, this tail is big. And it was only recently that astronomers learned just how big it was.
According to a paper published in 2024, this tail is at least 580,000 kilometers long, which is more than three times longer than the planet is wide. And to figure that out, astronomers used the Keck observatory in Hawaii to hunt not for sodium, or for the occasional x-ray, but for a helium signature buried in the infrared. Which is actually a novel technique for exoplanet tail hunting.
Past research had focused on an ultraviolet hydrogen signal, instead. But that signal isn’t visible from below Earth’s atmosphere, which Keck very much is. Plus, when you use a space-based telescope, you have to worry about your data getting muddied by a bunch of hydrogen that’s floating around in space but not a part of the tail you’re trying to study.
So switching to helium, when you’ve got a planet that’s mostly made of hydrogen and helium, seems like a good way to go. However you’re looking at this particular tail, it’s clear a lot of matter is being blasted off. About one Earth’s worth every billion years.
But given that WASP-69b is about 90 Earth masses, no one has to worry about it completely blowing away. At least not anytime soon. And because astronomers have managed to find another rare exoplanet that’s actively being stripped of its atmosphere, they can watch a strange form of planetary evolution happen in real time.
In fact, WASP-69b and its super long tail may help provide answers to a few outstanding mysteries. For example, most of the worlds that we’ve spotted super close to their stars are either small rocky worlds or Jupiter-sized gas giants. There’s an apparent dearth of so-called Hot Neptunes, and astronomers aren’t exactly sure why.
But however long it takes to answer that question, we can safely assume that WASP-69b will still be around to congratulate us. Now so far, we’ve been talking about stars creating tails by blowing a bunch of stuff off of other, much smaller objects. But it turns out, stars aren’t just the engines behind tails.
They can grow them, too! Or, at least, one can. Meet Mira, a binary star system that’s home to a dying red giant called Mira A, and its dead white dwarf companion Mira B.
And as they traverse interstellar space together, Mira A is shedding a bunch of mass and making a real pretty tail that clocks in at about 13 light years long. For comparison, that’s about three times the distance between our solar system and the next one over. The tail formed because the Mira binary is traveling a bit faster through space than all the stuff around it, called the interstellar medium.
Well, it's not just a bit faster. Mira is more like the stellar version of supersonic jet, creating a bow shock and wake as it plows through space. And remember how Pluto’s tail creates x-rays?
Particles from different sources colliding with each other and all that? Well, Mira’s situation isn’t completely different. Basically, you’ve got a bunch of super hot electrons coming out the bow shock mixing with the cooler hydrogen molecules in the wake that Mira is shedding.
Collisions between the two excites a bunch of those hydrogen molecules, which have to glow in order to relax back to their regular state. But unfortunately, this glow isn’t visible to the human eye. Mira’s tail shines in the ultraviolet part of the electromagnetic spectrum. But luckily for us, we have telescopes that can see UV light.
And the one that captured it is called GALEX. GALEX is an all-sky surveyor, which means it scans huge swaths of sky and astronomers peruse the resulting images to see if anything cool pops up. And Mira’s tail is one of those cool things!
Back in 2006, a team just happened to be looking at some incoming data, and found a smudgy patch of light in Mira’s vicinity. Something that looked more like a nebula than anything else. So they looked closer.
And voila! Other astronomers followed up on that accidental discovery, too. And a year after the first paper about Mira’s tail was published, there was one about what it looks like to a radio telescope.
So now that we know Mira’s tail is there, it can help teach us about what might happen to other stars that aren’t massive enough to end their lives in a violent supernova. And yes, that includes the Sun. But luckily for us, we’ll be long gone by the time our star balloons into a red giant and maybe grows a tail of its own.
To any aliens out there though, looking our way, I hope they see something spectacular. And you know what else is spectacular? The limited edition pin we're selling this month.
You can purchase your very own tiny version of Pluto, tail included, by heading over to dftba.com/SciShow And thanks for watching. [♪ OUTRO]
I mean that tail? Spectacular.
You’re not gonna find those anywhere else. Or are you? Well to human eyes, from Earth’s vantage point, the tail of a great comet can’t be beat.
But comets are far from the only cosmic bodies that can grow a tail. Here are five other cosmic wonders that leave a little bit of themselves behind as they careen through space. [♪ INTRO] In the grand scheme of the universe, comets and asteroids are pretty similar. I mean, asteroids are generally more rocky, and comets are more icy, but they’re both small clumps of stuff left over from our solar system forming a bunch of planets.
But comets are known for growing tails when they get too close to the Sun, and asteroids are not. When our Sun heats up a comet, a bunch of ice and dust get vaporized into a sort of temporary atmosphere called a coma. That coma is then blasted off the space rock by solar radiation to create a vibrant and reflective light show.
But there’s nothing stopping an asteroid from having stuff that the Sun can blast away, too. So several asteroids in our solar system are known to have comet-like traits. And one classic example is Phaethon, which has shed so much material over the eons that its debris cloud is thought to be the source of the Geminid meteor shower.
Usually, making a meteor shower debris cloud is a comet’s job. But you try telling Phaeton what to do. Astronomers have known about Phaethon’s tail since 2009.
And for a long time, they assumed it was made out of dust. Which makes sense, right? Comets have tails full of dust, and Phaethon likes to cosplay as a comet.
But upon closer inspection, Phaethon’s tail was way too robust to be made of just dust. So, there had to be something else going on. And eventually, astronomers managed to figure out that the tail was mostly made of sodium vapor.
See, Phaethon doesn’t just get a bit too close to the Sun. It gets closer to the Sun than Mercury, and far closer than any other notable asteroid ever does. And because it gets so close, it gets so hot that sodium inside the asteroid gets turned into a vapor, and eventually leaks up through the rest of the rock until it escapes and gets shaped into a tail.
Since comets can also release sodium vapor, you’d think we would have figured out this was happening to Phaethon a while ago. But no, the paper that actually proved it was happening was published in 2023. And although the paper answered one question, it raised others.
Like, if it’s not trailing a bunch of dust and pebbles and such, how did Phaethon make the debris cloud that the Geminids are coming from? The team did have a possible answer to that: Maybe there was some ancient collision between Phaethon and another body. But what that body was, and when that collision happened is still just a bunch of shrug emojis.
And Phaethon isn’t the only solar system body rocking a sodium-powered tail. As I mentioned before, comets can shoot out sodium vapor. But our next entry is a tag team of two much, much larger objects.
They’re so large their gravity has smushed them each into spheres. Dead, dark grey spheres. Of course I’m talking about Mercury and the Moon.
Mercury’s sodium tail was discovered back in 2001. And just like Phaethon, it's produced by the Sun’s heat. But it does have its own mystery.
Because Mercury’s tail isn’t at its brightest when it’s closest to the Sun. It’s actually brightest exactly 16 Earth days after that. And astronomers don’t know why.
Meanwhile, our moon is much further away, but that doesn’t stop it from shedding a bunch of sodium that the Sun’s radiation shapes into a long tail, too! And since the Moon orbits the Earth, there are a few days each lunar month… a few days around each New Moon… where our planet actually passes through that tail. During this time, the Earth’s gravity even causes some of that sodium to narrow in on a particular part of the sky.
And because sodium glows a particular shade of yellow, this means we see a greater concentration of yellow light in one patch of sky, about five times bigger than the Moon appears to be. Astronomers call it the Sodium Moon Spot. But before you get your hopes up, its light is way too dim for you to see it with the naked eye.
But it’s worth mentioning that the Moon’s tail isn’t just made out of sodium. Nor is Mercury’s. Sodium is just better at making its presence known, in the form of that yellow light.
And that makes it a good way to study the tail as a whole. For example, scientists want to understand how Mercury’s barely-there atmosphere changes as the Sun gets more or less active throughout the year. And as far as our lunar companion goes, studying the Sodium Moon Spot can help astronomers understand what’s creating the Moon’s tail at all.
Because according to research published in 2021, the spot doesn’t seem to get brighter when the Sun is more active. It does get brighter when the lunar surface is getting pelted by more micrometeoroids, though. So maybe its origin story is a bit different from Mercury’s, despite the two bodies looking so similar at first glance.
But lest you think tails are an Inner Solar System phenomenon, let’s turn our attention to Pluto. Because if any rock in the solar system is going to have a tail, it had better be the one that shares its name with a cartoon dog. When the New Horizons spacecraft flew by in 2015, astronomers got an up-close-if-not-personal look at Pluto’s tail.
And despite the dwarf planet being basically five billion kilometers from the center of the solar system, our Sun is still up to its old tricks. Its radiation is definitely a lot more spread out at those distances, but there’s still enough to smash into Pluto’s thin atmosphere and push molecules like nitrogen and methane into a tail. And on top of that, the collisions between the Sun’s particles and Pluto’s can knock electrons from one particle over to another.
It’s a process called charge exchange, and those electrons wind up having so much excess energy that they have to emit x-rays in order to calm down. I mean, as much as a subatomic particle can experience a sense of calm. It’s these x-rays that researchers used to discover Pluto’s tail in the first place.
But they started hunting for it before New Horizons made its closest approach. See, astronomers already knew that comets give off x-rays for the exact same reason. So in 2014, they used the Chandra X-ray Observatory to see if Pluto had them, too.
And after staring straight at Pluto for almost 10 hours, Chandra captured a whopping two x-rays. Which sounds like nothing. But it’s not.
It’s two more than nothing. And two whole x-rays can be a significant amount to an x-ray astronomer. But by combining that Chandra research with New Horizons’ data, scientists stumbled into a bit of a mystery: Pluto’s tail seems to be too bright.
Because while it’s shedding enough atmosphere into its tail, the Sun’s influence shouldn’t be strong enough to create that many x-rays. This could just mean that Pluto’s tail is actually bigger than New Horizons measured it to be. Or maybe there are some weird magnetic goings on in the region that are funneling the Sun’s radiation toward Pluto.
We’ll have to wait for a more sensitive x-ray telescope to take a look. Which…could be a while, so let’s move on to a tail that is way more impressive than anything a dwarf planet could hope to wag. This is WASP-69b, or at least an artist’s rendition of WASP-69b.
It’s roughly 160 light years away. And it orbits so close to its star, one of its years lasts less than four of our days. Given what we’ve learned about our Sun and bodies like Phaethon and Mercury, it should come as no surprise that WASP-69b’s star is slowly stripping off the exoplanet’s atmosphere and turning it into a tail.
But WASP-69b is a gas giant that’s larger than Jupiter, and about as massive as Saturn. So unlike Phaethon and Mercury, this tail is big. And it was only recently that astronomers learned just how big it was.
According to a paper published in 2024, this tail is at least 580,000 kilometers long, which is more than three times longer than the planet is wide. And to figure that out, astronomers used the Keck observatory in Hawaii to hunt not for sodium, or for the occasional x-ray, but for a helium signature buried in the infrared. Which is actually a novel technique for exoplanet tail hunting.
Past research had focused on an ultraviolet hydrogen signal, instead. But that signal isn’t visible from below Earth’s atmosphere, which Keck very much is. Plus, when you use a space-based telescope, you have to worry about your data getting muddied by a bunch of hydrogen that’s floating around in space but not a part of the tail you’re trying to study.
So switching to helium, when you’ve got a planet that’s mostly made of hydrogen and helium, seems like a good way to go. However you’re looking at this particular tail, it’s clear a lot of matter is being blasted off. About one Earth’s worth every billion years.
But given that WASP-69b is about 90 Earth masses, no one has to worry about it completely blowing away. At least not anytime soon. And because astronomers have managed to find another rare exoplanet that’s actively being stripped of its atmosphere, they can watch a strange form of planetary evolution happen in real time.
In fact, WASP-69b and its super long tail may help provide answers to a few outstanding mysteries. For example, most of the worlds that we’ve spotted super close to their stars are either small rocky worlds or Jupiter-sized gas giants. There’s an apparent dearth of so-called Hot Neptunes, and astronomers aren’t exactly sure why.
But however long it takes to answer that question, we can safely assume that WASP-69b will still be around to congratulate us. Now so far, we’ve been talking about stars creating tails by blowing a bunch of stuff off of other, much smaller objects. But it turns out, stars aren’t just the engines behind tails.
They can grow them, too! Or, at least, one can. Meet Mira, a binary star system that’s home to a dying red giant called Mira A, and its dead white dwarf companion Mira B.
And as they traverse interstellar space together, Mira A is shedding a bunch of mass and making a real pretty tail that clocks in at about 13 light years long. For comparison, that’s about three times the distance between our solar system and the next one over. The tail formed because the Mira binary is traveling a bit faster through space than all the stuff around it, called the interstellar medium.
Well, it's not just a bit faster. Mira is more like the stellar version of supersonic jet, creating a bow shock and wake as it plows through space. And remember how Pluto’s tail creates x-rays?
Particles from different sources colliding with each other and all that? Well, Mira’s situation isn’t completely different. Basically, you’ve got a bunch of super hot electrons coming out the bow shock mixing with the cooler hydrogen molecules in the wake that Mira is shedding.
Collisions between the two excites a bunch of those hydrogen molecules, which have to glow in order to relax back to their regular state. But unfortunately, this glow isn’t visible to the human eye. Mira’s tail shines in the ultraviolet part of the electromagnetic spectrum. But luckily for us, we have telescopes that can see UV light.
And the one that captured it is called GALEX. GALEX is an all-sky surveyor, which means it scans huge swaths of sky and astronomers peruse the resulting images to see if anything cool pops up. And Mira’s tail is one of those cool things!
Back in 2006, a team just happened to be looking at some incoming data, and found a smudgy patch of light in Mira’s vicinity. Something that looked more like a nebula than anything else. So they looked closer.
And voila! Other astronomers followed up on that accidental discovery, too. And a year after the first paper about Mira’s tail was published, there was one about what it looks like to a radio telescope.
So now that we know Mira’s tail is there, it can help teach us about what might happen to other stars that aren’t massive enough to end their lives in a violent supernova. And yes, that includes the Sun. But luckily for us, we’ll be long gone by the time our star balloons into a red giant and maybe grows a tail of its own.
To any aliens out there though, looking our way, I hope they see something spectacular. And you know what else is spectacular? The limited edition pin we're selling this month.
You can purchase your very own tiny version of Pluto, tail included, by heading over to dftba.com/SciShow And thanks for watching. [♪ OUTRO]